Gelatin compositions containing an aldehyde type hardener and an aliphatic monocarboxylic acid



United States Patent O 3,497,358 GELATIN COMPOSITIONS CONTAINING AN ALDEHYDE TYPE HARDENER AND AN ALI- PHATIC MONOCARBOXYLIC ACID Albert L. Sieg and Merrill W. Killick, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed May 3, 1965, Ser. No. 452,880 Int. Cl. G03c 1/30; C(Wh 5/00 US. Cl. 96111 8 Claims ABSTRACT OF THE DISCLOSURE The gelatin hardening effects of aldehyde-type gelatin hardeners is increased without any increase in proportion of the aldehyde hardener if a water soluble salt of an unsubstituted carbon acid having no more than 10 carbon atoms is used in combination with the aldehyde-type hardener. Formaldehyde, mucochloric acid, dihydroxydioxane and glutaraldehyde, for example, are illustrative of the aldehyde-type hardeners. The sodium salts of acetic acid, formic acid, oxalic acid, benzoic acid, carbonic acid, phthalic acid and adipic acid are illustrative of the water soluble salts of an unsubstituted carbon acid.

This invention relates to the hardening of photographic gelatin layers by the combination of an aldehyde-type hardener and a water soluble salt of a carbon acid.

In the coating of photographic gelatin layers including those having a silver halide component therein, it is often desirable to incorporate a material in the coating composition which will impart a hardening elfect to the gelatin in layer form. One of the most common types of hardeners for gelatin is an aldehyde-type compound included among which is formaldehyde, mucochloride acid, dialdehyde starch, dihydroxydioxane, glutaraldehyde, and dialdehyde plant gums. In the use of some of these hardeners, it is desirable to employ no more than a certain restricted proportion because of the effect some of these compounds might have upon certain photosensitive emulsion layers. This is particularly true in the case of formaldehyde which in excessive amount acts in a harmful manner upon certain photographic emulsions.

The prior art has mentioned the use of compounds such as dihydroxybenzene derivatives, active methylene compounds or the like for acceleration effect of aldehyde hardeners, however, these compounds generally are undesirable either because of stain characteristics or because of undesirable photographic characteristics of one kind or another.

One object of our invention is to make possible an increase in the amount of hardening obtained with a given amount of formaldehyde in a gelatin photographic layer. Another object of our invention is to provide a means of increasing the hardening from formaldehyde when used in gelatin layers without being accompanied by stain. A further object of our invention is to provide a means of increasing the degree of hardening imparted by an aldehyde hardener in a gelatin composition without developing undesirable photographic effects such as tone changes and increased fog levels. A still further object of our invention is to provide gelatin coating compositions having therein aldehyde hardener and a water soluble salt of a carbon acid which exerts a synergistic effect upon the hardening characteristics of the aldehyde hardener. Other objects of our invention will appear herein.

We have found that the gelatin hardening effects of aldehyde-type hardeners is increased without any increase in proportion of the aldehyde hardener if there is employed therein a water soluble salt of an unsubstituted 3,497,358 Patented Feb. 24, 1970 carbon acid having no more than 10 carbon atoms. This includes both the water soluble alkali metal salts, the water soluble alkaline earth metal salts and the water soluble ammonium or amine salts of the carbon acids in accordance with the invention. The acids whose salts have been found to be effective in this connection are the unsubstituted carbon acids composed only of C, H and 0 such as those found in one or the other of the following categories:

(1) the aliphatic monocarboxylic acids having no more than 10 carbon atoms,

(2) carbonic acid,

(3) benzenoid dicarboxylic acids and aliphatic dicarboxylic acids having no more than 10 carbon atoms,

(4) aromatic carboxylic acids.

The following list is a group of acids, the salts of which have been found to increase the hardening properties of the aldehyde in accordance with our invention: acetic acid, formic acid, oXalic acid, benzoic acid, propionic acid, butyric acid, carbonic acid, caprylic acid, malonic acid, phthalic acid, adipic acid, etc.

Our invention is useful in hardening various types of gelatin and is particularly effective on pigskin gelatin, however, other types of gelatin such as bone belatin, hide gelatin and the like are also included. For photographic uses ordinarily the gelatin has a jelly strength of not less than 50 grams bloom and it is gelatins of good jelly strength which are particularly useful in the compositions in accordance with the invention. In the compositions in accordance with the invention there should be incorporated at least 1% of the salts based on the weight of the gelatin, the preferable proportion of salts being within the range of 5-15% based on the weight of the gelatin. The gelatin coating compositions employed for applying photographic gelatin layers in accordance with the invention are aqueous in nature but can tolerate up to as much as 10% of water soluble solvents such as alcohol, acetone or the like.

The following examples illustrate the advantages of the invention but it is to be understood that the invention is not limited thereby.

EXAMPLE 1 A sample of pigskin gelatin of good jelly strength was dissolved in water to produce a solution of which the gelatin is 10% by weight. 0.5% of formaldehyde based on the dry weight of the gelatin was added to the solution. The solution was then separated into five equal parts and the following variations were made:

(A) 10% gelatin so1ution+0.5% formaldehyde, based on dry gelatin.

(B) Same as (A) +5% sodium acetate based on dry gelatin.

(C) Same as (AH-10% sodium acetate based on dry gelatin. 4 (D) 10% gelatin solution+l0% sodium acetate but no formaldehyde.

(E) 10% gelatin solution alone.

These solutions were each coated on a formaldehydefree baryta coated paper and were air dried overnight. The brush-off point of each sample was determined. The brush-off point is a melting point determination carried out under mildly abrasive conditions. The higher the temperature of brush-off, the harder and stronger the layer is. The brush-off point method of testing gelatin layers involves submerging the sample coated with the gelatin layer in water and raising the temperature at the rate of 5 F. per minute from room temperature to 212 F. In the test each sample is brushed after every 3 degree rise in temperature with a mechanical brushing device. The temperature selected as the end point is that at which the brush removes the gelatin coating from its support. The same measurement was repeated after 10 days aging at room conditions. The results obtained were as follows:

Brush-off, Brush-off, fresh, F. 10 days F.

EXAMPLE 2 To two types of photographic silver halide gelatin emulsions, various levels of formaldehyde and carboxylic acid salts were added. These emulsions were then coated onto a formaldehyde-free baryta coated paper support. The coatings were air dried overnight. The brush-off points were determined both fresh and after 10 days aging and these points were tabulated as follows:

dict hardening obtained by the hardener upon a photographic gelatin layer. The results which were obtained are as follows:

Moles of salt/100 g. Hardening Salt dry gelatin index (see) 0. 1 200 Sodium oxalate 0. 1 372 Sodium benzoate 0.1 343 Percent formalde- Percent hyde based salt based BOP BOP Emulsion on dry on dry fresh 10 days ype gelatin Salt used gelatin T. T.

AgOl 0. 25 Sodium acetate 0. 82 82 AgCl 0.25 do 5.0 s3 84 A1501 0. 25 do 10.0 85 80 AgCl 0.50 do 0.0 85 85 AgCl 0. s0 5. 0 86 87 AgCl 0. 50 0 86 103 AgOlBr 0.25 0.0 83 84 AgOlBr 0. 5. 0 88 80 AgOlBr 0. 25 10. 0 90 88 AgClBr 0. 25 20.0 95 95 AgClBr 0. 0. 0 s7 88 .AgClBr 0. 50 5. 0 90 94 AgClBr 0. 50 10. 0 92 03 AgClBr 0. 50 20. 0 98 100 AgClBr 0. 25 0. 0 83 86 .AgClBr 0. 25 5. 0 89 92 AgClBr 0. 25 10.0 89 90 AgOlBr 0. 25 20. 0 92 95 AgClBr 0. 5O 0. 0 89 90 AgClBr 0. 50 5. 0 91 04 AgClBr 0. 50 10. 0 94 104 AgClBr 0. 50 20.0 104 10s EXAMPLE 3 A silver cholrobromide gelatin emulsion was coated gg g g Salt gggg gg onto a support and hardened with formaldehyde used at Ed N 1 e one 206 the level of 0.5% formaldehyde based on the welght of 50 DO" Potassium acetate 188 the dry gelatm. The varlatlons were as follows: Do N0 203 Do Potasslum acetate..- 190 (F) Normal emulsion-l-normal hardener g g g g5 (G) Same as q of sodipm acetate Bon 3:: %n f.-.i f::-. 12:: 213 (H) Same as (A) -|-h1gh level of sod1um acetate. jg acetate-U Brush-off points were determined fresh and after seven 3g" agtassimn acetatefl days incubation at 120 F. and 35% RH. The results DO:: III POtaSQEIHaEGEaiII" I: 179 D0 None 629 Obtalned were as follOWS- D0 Potassium acetate 219 BOP 7 days Sample BOP Fresh (F.) incubation (I.)

102 136 Our 1nvent1on is effective not only for hardening gelatm 143 179 in cases where the gelatin is the sole polymeric material 186 194 present, but is also effective in compositions in which gelatin is mixed with some other polymeric material such EXAMPLE 4 as those cases where gelatin comprises at least 30% of the A 10% by weight solution of pigskin acid processed gelatin was prepared to which was added various types of carboxylic acid salts compared with a case where no salt was added. The hardening index was determined. In this method the time in seconds it takes a gelatin to obtain a standard viscosity as hardener it being added at the rate of 0.2 cc. of 40% formaldehyde solution per minute was determined. The shorter time indicates the greater speed of formaldehyde cross-linking taking place in the gelatin. This has been found to be a reliable test to precomposition. For example, in coating compositions in which the polymeric material is composed of equal parts of gelatin and an alkyl acrylate-acrylic acid copolymer and in which is incorporated a hardener in accordance with our invention, an increased degree of hardness is obtained compared with the hardness obtained using the aldehyde hardener alone.

The invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

We claim:

1. A composition of matter consisting essentially of high jelly strength gelatin, a hardening amount of a gelatin hardener selected from the group consisting of formaldehyde, mucochloric acid, dialdehyde starch, dihydroxydioxane, glutaraldehyde and dialdehyde plant gums and a Water soluble salt of an aliphatic monocarboxylic acid having 1 to carbon atoms.

2. A composition of matter consisting essentially of high jelly strength gelatin, a hardening amount of formaldehyde and a Water soluble salt of an aliphatic monocarbxoylic acid having 1 to 10 carbon atoms.

3. A composition of matter consisting essentially of high jelly strength gelatin, a hardening amount of formaldehyde and an alkali metal salt of an aliphatic monocar' boxylic acid having 1 to 10 carbon atoms.

4. A composition of matter consisting essentially of high jelly strength gelatin, a hardening amount of formaldehyde and sodium acetate.

5. A photographic silver halide gelatin emulsion containing a hardening amount of a gelatin hardener selected from the group consisting of formaldehyde, mucochloric acid, dialdehyde plant gums and a water soluble salt of an aliphatic monocarboxylic acid having 1 to 10 carbon atoms.

6. A photographic silver halide gelatin emulsion containing a hardening amount of formaldehyde and a water soluble salt of an aliphatic monocarboxylic acid having 1 to 10 carbon atoms.

7. A photographic silver halide gelatin emulsion containing a hardening amount of formaldehyde and an alkali metal salt of an aliphatic monocarboxylic acid having 1 to 10 carbon atoms.

8. A photographic silver halide gelatin emulsion containing a hardening amount of formaldehyde and sodium acetate.

References Cited UNITED STATES PATENTS 7/1939 Sheppard et a1. 96-111 X 7/1967 Welch 96l11 X US. Cl. X.R.

3;; UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No Dated 2 Inven[or(5) Albert L- and Merrill w. Killick It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 1 "acid, dialdehyde plant gums and a water soluble. salt of an" should read -ac id, dialdehyde starch, dihydroxydioxane glufaraldehy and dialdehyde plant gums and a water soluble sal r oi an- Signcd and sealed this 1st day of September 1970 (SEAL) Attest:

EDWARD M. FLETCHER,JR. WILLIAM 1i. SCHUYLER, JR. Attostlng Offlcer Comlni ssione'r of Patents 

